WASHINGTON - Amtrak is planning to buy next-generation high-speed trains and will scrap plans to add passenger cars to its Acela Express fleet, its president told lawmakers Thursday.

"They're too expensive, and what we really need to do is replace the Acela with new sets of trains," Amtrak President and CEO Joseph Boardman told members of the House Transportation and Infrastructure Committee.

The federally subsidized railroad will begin collecting information next year to eventually start replacing its 20 Acela Express trains and add an undetermined number of extra trains. The railroad wants to expand seating capacity and provide for more frequent high-speed service on the Northeast Corridor between Washington and Boston.

An earlier plan to add 40 new passenger cars with newer technology to the older Acela trains posed technical challenges and wasn't cost-effective, according to Amtrak. It also wouldn't have been able to accommodate increasing ridership, the railway said.

In fiscal 2012, Amtrak set a new record of 11.4 million riders on the Northeast Corridor, and a national ridership record of 31.2 million passengers.

"Moving directly to new high-speed train sets is the best option to create more seating capacity, permit higher speeds and maximize customer comfort, all while improving equipment reliability and reducing operating costs," Boardman said in a statement.

An Amtrak official said a funding source for the new trains hasn't been determined.

Amtrak should put off buying new equipment until it figures out what kind of system it will have, Republican Rep. John Mica of Florida, outgoing chairman of the Transportation and Infrastructure Committee, said during an interview.

Congressional oversight of future purchases is needed, given the litigation and design problems associated with the Acela acquisitions, Mica said.

"It's been a parade of horribles in past acquisitions," he said. "So I have to caution - when Amtrak does things, it often gets messed up."

Mica held Thursday's hearing to examine the future of high-speed rail in the Northeast Corridor, including the role of private-sector participation.

Amtrak is seeking federal funding to help build a $151-billion high-speed rail line between Washington and Boston over the next 30 years.

Mica says bringing in expertise from the private sector could speed the process.

"My premise is that it can be done in a third of the time and at much less cost," he said.